1. Field
A rechargeable lithium battery is disclosed.
2. Description of the Related Art
Lithium rechargeable batteries have recently drawn attention as a power source for small portable electronic devices. They use an organic electrolyte and thereby have twice the discharge voltage of a conventional battery using an alkali aqueous solution, and accordingly have high energy density.
As for a positive active material for a lithium rechargeable battery, lithium-transition metal oxides being capable of intercalating lithium, such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1), and the like, have been researched. As for a negative active material for a lithium rechargeable battery, various carbon-based materials such as artificial graphite, natural graphite, and hard carbon capable of intercalating and deintercalating lithium ions have been used.
Since graphite among the carbon-based materials has a low discharge potential relative to lithium of about −0.2V, a battery using graphite as a negative active material has a high discharge voltage of about 3.6V and excellent energy density.
Furthermore, graphite typically provides a long cycle life for a battery due to its outstanding reversibility, so graphite is often used as a negative active material. However, graphite negative active materials have a low density (e.g., a theoretical density of about 2.2 g/cc) and, consequently, a low capacity in terms of energy density per unit volume.
Further, a battery including a graphite negative active material may swell, which may result in decreased capacity, because graphite is likely to react with an organic electrolyte at a high discharge voltage. In order to solve (or lessen) these problems, a great deal of research on an oxide negative active material such as tin oxide, lithium vanadium-based oxide, and the like has recently been performed. However, those oxide negative active materials still do not realize sufficient cell performance.